I'm sorry to hear about your neck issues. I've lived with them on and off for 45 years, so you have my sympathy.
However, I don't believe a lighter bike wil, have a very material effect, since your real issue is windage because of the upright position.
Even though it's been a while, I suggest you try to stay positive, and get a new consult and/or some physical therapy, and see if and how far you can work toward a more normal riding posture.
I don't know how old you are, but I was in my twenties when I damaged my neck, and it slowly improved over 10 years to where I barely notice it riding. But early on it didn't look that promising, and it was a long slow process before I could ride without serious and lasting neck pain.
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